2′,3′-dideoxyinosine, which is also known as didanosine or ddI, is an acid labile drug which will degrade in the stomach. Didanosine has the following structural formula.

Didanosine is known to be effective in the treatment of patients with the HIV virus by inhibiting HIV replication. Furthermore, ddI has become widely used as a component of the therapeutic cocktails for treating AIDS.
Didanosine is generally available in a variety of oral dosages, including Chewable/Dispersible Buffered Tablets in strengths of 25, 50, 100 or 150 mg of didanosine. Each tablet is buffered with calcium carbonate and magnesium hydroxide. Didanosine tablets also contain aspartame, sorbitol, microcrystalline cellulose, Polyplasdone®, mandarin-orange flavors and magnesium stearate. Didanosine Buffered Powder for Oral Solution is supplied for oral administration in single-dose packets containing 100, 167 or 250 mg of didanosine. Packets of each product strength also contain a citrate-phosphate buffer (composed of dibasic sodium phosphate, sodium citrate, and citric acid) and sucrose. A didanosine Pediatric Powder for Oral Solution is also available and which is supplied for oral administration in 4- or 8-ounce glass bottles containing 2 or 4 grams of didanosine respectively, and is to be mixed with commercial antacid before oral ingestion.
With particular emphasis on the tablets, whether ingested alone or as part of a combination (“cocktail”) therapy regimen, the current chewable/dispersible buffered tablets are not conducive from a patient ease of use standpoint. Whereas the other products which are a part of the AIDS therapeutic cocktail are capsules or tablets and easily swallowed, the ddI Chewable/Dispersible Buffered Tablets must be thoroughly chewed or uniformly dispersed in water before administration.
Because ddI degrades rapidly at acidic pH, ddI, in its chewable/dispersible form and its buffered powder for oral solution form, contains buffering agents and is administered with antacids in the pediatric powder form. However, the presence of the large quantities of antacid components in the formulation can lead to significant GI imbalance as noted by severe diarrhea. Many patients also complain about chewing the large ddI tablets (a single dose is two tablets of 2.1 g each), the taste of the ddI or the time required to disperse the tablets and the volume of fluid (4 oz) required for the dose. As the current adult dose is 200 mg ddI, twice a day, or a single dose of 400 mg ddI daily, a high ddI load formulation without antacid or buffers is necessary to avoid the discomforting side effects and difficulty of administering the current ddI compositions.